CA2441079C - Process for production of butyl rubber - Google Patents

Abstract

The present invention relates to a process for producing polymers comprising repeating units derived from at least one isoolefin monomer, optionally repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers in the presence of a zinc compound and optionally an organic halide activator.

Description

PROCESS FOR PRODUCTION OF BUTYL. RUBBER
FIELD OF THE INVENTION
The present invention relates to a process for producing polymers comprising repeating units derived from at Least one isoolefin monomer, optionally repeating units derived from at least one multiolefin monomer and optionally fizrther copolymerizable monomers in the presence of a zinc compound.
BACKGROUND OF THE INVENTION
Butyl rubber is understood to be a copolymer of an isoolefin and one or more, preferably conjugated, multiolefins as comonomers. Commercial butyl comprise a major portion of isoolefin and a minor amount of a conjugated multiolefin. The preferred isoolefin is isobutylene.
Butyl rubber or butyl polymer is generally prepared in a slurry process using methyl chloride as a vehicle and a Friedel-Crags catalyst as part of the polymerization 1 S initiator. The polymerization is generally carried out at temperatures of about -90°C to -100°C. See U.S. Patent No. 2,356,128 and Ullmanns Encyclopedia of Industrial Chemistry, volume A 23, 1993, pages 288-295. The lc>w polymerization temperatures are required in order to achieve molecular weights which are sufficiently high for rubber applications.
Other compounds that have been found to be active as catalysts for polymerizing isoolefins include organometallics compounds in combination with a cation-generating agent, such as CSMeSTiMe~/B(C6F5)3 (WO-00/04061-A1), Cp2AIMelB(C6F5)3 (US-5,703,182), and combinations of zirconocenes and related complexes with either B(C~FS)3 or CPh3[B(C6F5)4] (WO-95/29940-Al, DE-A1-198 36 663), Song, X.; Thornton-Pett, M.; Bochmann, M. Organometallics 1998, 17, 1004, Carr, A. G.; Dawson, D. M.; Bochmann, M. Mac~omol. ~Zapid Commun. 1998, 19, 205.
Zinc compounds have not been used as catalysts for isoalkene polymerizations.
Indeed, ZnCl2 in the presence or absence of alkyl halide activators (such as Me3CCl or MeCOCI) and used either in neat isobutene or in isobutene/methyl chloride mixtures, proves to be inactive, and no polymer is obtained.

Pos i 14s ca In one aspect, the present invention provides a process for producing polymers comprising repeating units derived from at least one isoolefin monomer, optionally repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers in the presence of a zinc compound.
In another aspect, the present invention provides a slurry process for producing polymers comprising repeating units derived from at least one isoolefin monomer, optionally repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers in the presence of a zinc compound.
In still another aspect, the present invention provides method for catalysing the polymerization of a monomer mixture comprising at least one isoolefin monomer, optionally at least one multiolefin monomer and optionally further copolymerizable monomers by addition of a zinc compound.
DET~4ILED DESCRIPTION OF THE IN~IENTION
The present invention relates to isoolefin polymers and butyl rubber. The terms "butyl rubber", "butyl polymer" and "butyl rubber polymer" are used throughout this specification interchangeably. While the prior art in using butyl rubber refers to polymers prepared by reacting a monomer mixture comprising a C4 to C7 isomonoolefin monomer and a C4 to C~4 multiolefin monomer, this invention specifically relates to polymers comprising repeating units derived from at least one isoolefin monomer, optionally repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers.
The invention is not limited to a special isoolefin. Isomonoolefins are preferred.
Preferably the isoolefin(s) have in the range of from 4 to 16 carbon atoms, in particular 4-7 carbon atoms, such as isobutene, 2-methyl-1-butene, 3-methyl-1-butene, 2-methyl-2-butene, 4-methyl-1-pentene and mixtures thereof: Most preferred is isobutene.
The invention is not limited to a special multiolefin. Every multiolefin copolymerizable with the isoolefin known by the skilled in the art can be used.
However, multiolefins with in the range of from 4-14 carbon atoms, such as isoprene, butadiene, 2-methylbutadiene, 2,4-dimethylbutadiene, piperyline, 3-methyl-1,3-pentadiene, 2,4-hexadiene, 2-neopentylbutadiene, 2-methyl-1,5-hexadiene, 2,5 dimethyl-2,4-hexadiene, 2-methyl-1,4-pentadiene, 2-methyl-1,6-heptadiene, cyclopentadiene, methylcyclopentadiene, cyclohexadiene, 1-vinyl-cyclohexadiene and mixtures thereof, in particular conjugated dimes, are preferably used.
Isoprene is particularly preferably used.
As optional monomers every monomer copolymerizable with the isoolefins and/or dienes known by the skilled in the art can be used. a,-methyl styrene, p-methyl styrene, chlorostyrene, cyclopentadiene and methylcyclopentadiene are preferably used.
Indene and other styrene derivatives may also be used in this invention.
Preferably, the monomer mixture comprises in the range of from 80% to 100%
by weight of at least one isoolefin monomer and in the range of from 0°/~ to 20°/~ by weight of at least one multiolefin monomer and in the range of from 0% to 5%
by weight of at least one further copolymerizable monomer. More preferably, the monomer mixture comprises in the range of from 85% to 99.5% by weight of at least one isoolefin monomer and in the range of from 0.5% to 15% by weight of a multiolefin monomer. Most preferably, the monomer mixture comprises in the range of from 95%
to 99% by weight of at least one isoolefin monomer and in the range of from 1 % to 5%
by weight of at least one multiolefin monomer.
The weight average molecular weight, MW, is preferably greater than 100 kg/mol, more preferably greater than 200 kg/mol, even more preferably greater than 300 kglmol.
The polymerization is performed in the presence of an zinc compound capable of initiating the polymerization process. The term "zinc compound" denotes a compound of composition ZnRlR2 comprising a Lewis acidic zinc metal centre bonded to two identical or different ~ 1 to CSo hydrocarbon radicals (R' and R2) which may be linear, branched or cyclic and may contain one or more non-carbon atoms in the carbon-chain at least one of which is electron withdrawing. Preferred ligands Ri and R2 are aryl groups or substituted aryl groups. Most preferably the ligands R' and R2 are pentafluorophenyl.
The zinc compound may be generated by known methods. For example, it is known in the art that Zn(C6F5)2 can be prepared by several methods, including the Pos 1 ia.6 cA

reaction of ZnCl2 with C6FSMgX (Noltes, J. G.; van den Hark, J. W. G. J.
Organomet.
Chem. 1963, 64, 377), from AgC6F5 and ZnI2 (Sartori, P.; Weidenbruch, M.
Chern. Ber.
1967, 100, 3016), by the thermal decarboxylation of Zn(02CC6FS)2 (Miller, W.
T.; Sun, K. K.; J. Am. Chem. Soc. 1970, 92, 6985), or by the reaction of ZnMe2 or ZnEt2 with B(C6F5)3 (Walker, D. A.; Woodman, T. J.; Hughes, D. L.; Bochmann, M.
Organometallacs 2001, 20, 3772). It may be advantageous to stabilize the zinc compound with at least one neutral ligand such as toluene, xylene, hexamethylbenzene and the like.
In one embodiment, the compound Zn(C6F5)2~toluene is synthesized by the exchange reaction of ZnR2 (R = Me or Et) with B(C6F5)3 in toluene.
In a preferred embodiment, the zinc compound is the only catalyst/initiator present in the monomer mixture.
The preferred ratio of zinconocene to monomers) is in the range of from 1:106 to 1:102 by mol, and the most preferred ratio is in the ra~yge of from 1:103 and 1:104.
It might be advantageous to further add co-catalyst(s) to the monomer mixture.
The invention is not limited to any special co-catalyst/activator as long as the co-catalytic compound does not adversely affect the polymerisation reaction.
Preferred are activators of the general formula R3CX (I) or RCOX (II) with each R
independently being a CI to Cso hydrocarbon radical which may be linear, branched or cyclic and may contain one or more non-carbon atoms in the carbon-chain, such as methyl, ethyl, n-propyl, n-propyl, n-butyl, s-butyl, t-butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, 3-methylpentyl and 3,5,5-trimethylhexyl and each X being a halogen, preferably chlorine or bromine. Most preferred co-catalysts are Me3CCl, MeCOCl, and Me3CBr.
The preferred ratio of zinc compound to co-catalyst(s) is in the range of from 1:0.1 to 1:10 by mol, and the most preferred ratio is in the range of from 1:1 to 1:3.
In one embodiment, the polymerization is preferably performed in a continuous process in slurry (suspension), in a suitable inert diluent. Inert diluents known to the person skilled in the art for butyl polymerization may be considered as the diluents (reaction medium). These comprise alkanes, chloroalkanes, cycloalkanes or aromatics, which are frequently also mono- or polysubstituted with halogens.
Hexane/chloroalkane mixtures such as hexaneldichloromethane, dichloromethane or methyl chloride itself are mentioned in particular. The preferred diluent is methyl chloride.
In another embodiment, the polymerization is preferably performed in the absence of a diiuent in bulk. More preferably, the the polymerization is performed in liquid/liquified monomer(s).
The monomers are preferably polymerized at temperatures in the range from -120°C to +20°C, preferably in the range from -100°C to -20°C, and pressures in the range from 0.1 to 4 bar.
The use of a continuous reactor as opposed to a batch reactor may have a positive effect on the process. Preferably, the process is conducted in at least one continuos reactor having a volume of between 0.1 m3 and 100 m3, more preferable between 1 m3 and 10 m3.
If polymerization is performed continuously, the process is preferably performed with the following three feed streams:
1 S I) solvent/diluent + isoolefin (preferably isobutene) + multiolefin (if present, preferably dime, isoprene) II) zinc compound III) organic halide activator (if present) Polymers comprising residual double bonds resulting from the inventive process may be the starting material for a halogenation process in order to produce halo-butyl polymers. Bromination or chlorination can be performed according to the procedures described in Rubber Technology, 3'~ Ed., Edited by Maurice Morton, Kluwer Academic Publishers, pp. 297 - 300 and references cited within this reference.
The copolymers presented in this invention are ideally suitable for the production of moldings of all kinds, in particular tyre components and industrial rubber articles, such as bungs, damping elements, profiles, films, coatings. The polymers are used to this end in pure form or as a mixture with other rubbers, such as NR, BR, HNBR, NBR, SBR, EPDM or fluororubbers. The preparation of these compounds is known to those skilled in the art. In most cases carbon black is added as f ller and a sulfur based curing system is used. For the compounding and vulcanization it is referred to Encyclopedia of Polymer Science and Engineering, Vol. 4, S. 66 et seq.
(Compounding) and Vol. 17, S. 666 et seq. (Vulcanization).
The vulcanization of the compounds is usually effected at temperatures in the range of 100 to 200°C, preferred 130 to 180°C (optionally under pressure in the range of 10 to 200 bar).
The following Examples are provided to illustrate the present invention:

Examples Equipment Isoprene content was determined through iH NMR spectroscopy with the use of a Bruker 300 MHz NMR Spectrometer. NMR samples used to determine isoprene content were prepared in CDCl3. Microstructure information was calculated with the use of previously established integration methods. Chemical shifts were referenced to a TMS internal standard.
GPC analysis was performed in tetrahydrofuxan at 25 °C with the use of a Polymer Lab GPC-220 gel permeation chromatograph equipped with a dual refractive index and PD2040 dual-angle light scattering detector and PL gel 2 x mixed bed-B, 30 cm, 10 micron columns.
Polymer gel content was determined through conventional gravimetric analysis of the dry, hydrocarbon-insoluble fraction (insoluble in boiling cyclohexane, under agitation for a period of 60 minutes) Chemicals Isobutene was obtained from BOC and dried by passing through 10 percent weight sodium on aluminum oxide and 4A molecular sieves.
Isoprene was obtained from Aldrich and purified by distillation from a sodium mirror under nitrogen prior to use t-Butyl chloride was obtained from Aldrich and purified by distillation from calcium hydride under nitrogen prior to use.
Acetyl chloride was obtained from Aldrich and used as received.
Dichloromethane was obtained from Riedel-de-I-Iaen (high purity grade) and purified by distillation from calcium hydride under nitrogen prior to use.
Zn(C6F5)2~toluene was synthesized by the exchange reaction of ZnMe2 with B(C6F5)3 in toluene. A solution of B(C6F5)~ (3.01 g, 5.88 mmol) in toluene (50 mL) was treated with a solution of ZnMe2 in toluene (4.41 mL, 8.82 mmol, 2 ~ at room temperature. The mixture was stirred for 30 minutes. Removal of volatiles left a white solid which was recrystallized from light petroleum (60 mL) at -20 °C
overnight to give Zn(C6F5)2~toluene as needle-like crystals, yield 3.33 g (76.6 %). Anal. Calcd.
for CizFloZmC~Hg: C, 46.42; H, 1.64. Found: C, 45.93; H, 1.46. 'H NMR (300 MHz, 25 °C, C6D6): s 6.98-7.13 (m, 5 H, Ph), 2.10 (s, 3 H, Me). 1gF (C6D6): ~ -118.3 (m, 4 F, o-F), -152.9 (t, 2 F, JFF = 19.8 Hz, p-F), -160.9 (m, 4 F, m-F).

Into a 250 mL 3-necked reaction flask, equipped with a magnetic follower and cooled to -78°C with a dry ice/acetone bath, was condensed 97 mL of isobutene. 3 mL
of isoprene and a solution of Me3CCl (18.5 mg, 0.2 mmol) in dichloromethane (2 mL) were added to the reactor vessel and then the mixture was allowed to equilibrate at -78°C.
Zn(C6F$)2~toluene (98 mg, 0.2 mmol) was dissolved in 2 mL of dichloromethane and then transferred by syringe into the rapidly stirred ( 1000 rpm) mixture.
After 30 min. the reaction was terminated by addition of methanol {10 mL).
The polymer was precipitated with 200 mL methanol, filtered and dried at SO°C to constant weight. The yield was 4.5 g, M" = 581,000 and MW = 1,306,000, with 2.7 mol-isoprene content and the gel quota of 1.5%.

Into a 250 mL 3-necked reaction flask, equipped with a magnetic follower and cooled to -78°C with a dry ice/acetone bath, was condensed 95 mL of dry isobutene. 5 mL of isoprene and a solution of Me3CCl (27.8 mg, 0.3 mmol) in dichloromethane (2 mL) were added to the reactor vessel. The mixture was stirred rapidly at -78 °C, and 148 mg (0.3 mmol) of Zn(C6Fs)2~toluene in 3 mL of dichloromethane were added.
After 30 min. the reaction was terminated by addition of methanol (10 mL). The polymer precipitated with 200 mL methanol and dried at 50°C to constant weight.
The yield of copolymer was 3.8 g, M" = 226,000 and MW = 661,000, with an isoprene content of 4.7 mol-% and a gel quota of 1.0%.

The methodology of Example 2 was repeated, except that 93 mL of isobutene and 7 mL of isoprene were used. The yield of copolymer was 4.0 g, M" = 302,000 and MW = 782,000. The isoprene content was 6.4 mol% and the gel quota 3.8%.

The methodology of Example 2 was repeated, except that 90 mL of isobutene and 10 mL of isoprene were used and the reaction time was 60 minutes. The polymer yield was 3.2 g, M" = 236,000 and MW = 592,000. The isoprene content was 9.0 mol%
and the gel quota 4.6%.

The methodology of Example 2 was repeated, except that Me3CBr (41.1 mg, 0.3 mmol) was used instead of Me3CCl. The reaction was left for 20 minutes. The polymer yield was 4.4 g, M" = 192,000 and MW = 359,000. The isoprene content was 5.1 mol-%.

Into a 250 mL 3-necked flask, equipped with a magnetic follower and cooled to -78°C with a dry ice/acetone bath, was condensed 70 mL of methyl chloride and 30 mL
of isobutene. 1.5 mL of isoprene and a solution of Me3CCl (27.8 mg, 0.3 mmol) in dichloromethane (2 mL) were added to the reactor vessel and the mixture was allowed to equilibrate at -78°C. A solution of 148 rng (0.3 mmol) of Zn(C6Fs)2~toluene in 3 mL
of dichloromethane was injected into the rapidly stirred mixture. After 20 min. the reaction was terminated by addition of methanol ( 10 mL). The polymer was precipitated with 20mL of methanol, filtered and dried in at 50°C to constant weight.
The yield was 1.7 g, M~, = 225,000 and MW = 405,000, with an isoprene content of 3.0 mol% and a gel quota of 0.6%.

The methodology of Example 6 was repeated, except that 2.1 mL of isoprene was used. 'The yield of copolymer was 1.5 g, M" = 100,000 and Mw = 241,000, with an isoprene content of 4.0 mol-% and a gel quota of 0.6%.

The methodology of Example 6 was repeated, except that 3.0 mL of isoprene was used. The polymer yield 0.8 g, Mn = 82,500 and MW = 198,000. The isoprene content was 5.2 mol-% and the gel quota 0.6%.

The methodology of Example 6 was repeated, except that 3.0 mL of isoprene and 55.6 mg (0.6 mmol) of Me3CC1 were used. 'The polymer yield was 1.0 g, Mn =
60,700 and MW = 288,000, with an isoprene content of 5.7 mol-%.

Into a 250 mL 3-necked reaction flask, equipped with a magnetic follower and cooled to -78°C with a dry ice/acetone bath, were condensed 70 mL of methyl chloride and 30 xnL of isobutene. 3.0 mL of isoprene and a solution of Me~CBr (82.2 mg, 0.6 mmol) in dichloromethane (2 mL ) were added and the mixture was allowed to equilibrate at -78°C. A solution of 148 mg (0.3 rnmol) of Zn(C6F5)2~toluene in 3 mL of dichloromethane was then transferred to the rapidly stirred mixture. The reaction was terminated after 30 minutes. The polymer was precipitated with 200 mL of methanol, filtered and dried at 50°C to constant weight. The yield was 1.5 g, Mn = 194,000 and MW = 612,000, with an isoprene content of 5.2 mol-%.

The methodology of Example 10 was repeated, except that 5.0 mL of isoprene was used. The yield of copolymer was 1.2 g, Mn = 215,000 and MW = 1,014,000.
'The isoprene content was 6.7 mol-%.

Following the procedure of Example 2, 2 mL I,3-pentadiene and 1.5 mmol Me3CBr in 2 mL dichloromethane were added to 100 mL isobutene at -78 °C. To this rapidly stirred mixture was added a solution of 0.3 mmol Zn(C6Fs)2~toluene in 3 mL of dichloromethane. The reaction was terminated after 30 min, the polymer was precipitated and dried to give a yield of 5.9 g, Mn = 100,000 and MW =
199,000. The pentadiene content was 2.5 mol%.

The procedure of Example 12 was followed, except that 4 mL of 1,3-pentadiene were added. The polymer yield was 3.4 g, Mn = 102,000 and MW = 172,000. The pentadiene content was 5.6 mol-%.
Examples 1 - 4 show us that the zinc compound, Zn(C6F5)Z~toluene, in combination with Me3CCI is an activate initiating system for the production of butyl rubber in an essentially solvent free system. Examples 1 --4 also show that wifih varying levels of isoprene in the feed a product with high levels of incorporated into the polymer can be made with a high molecular weight while maintaining a low level of gel.
Example 5 teaches us that Me3CBr can be used as a co-catalyst as well as Me3CCl for the production of butyl rubber.
Examples 6 - 9 teach us that the zinc compound, Zn(C6Fs)2~toluene, in combination with Me3CC1 can also be used to prepare high molecular weight butyl rubber in a solvent based system. The examples here using the industrially relevant MeCI as a solvent of choice. Taken in combination with examples 1 - 4 we can see the utility of the system, being able to produce a desirable product with or without the need for solvent.
Examples 10 and 11 teaches us that we can also utilise Me3CBr in the presence of a solvent and produce high molecular weight product.
Examples 12 and i 3 show that the zinc compound, Zn(C6Fs)2~toluene, in combination with Me3CC1 can not only polymerise isobutene and isoprene but isobutene and 1,3-pentadiene to produce a high molecular weight product.

Claims (8)

1. A process for producing polymers comprising: polymerizing monomer units comprising at least one isoolefin monomer in the presence of a zinc compound of the formula ZnR1R2, wherein the zinc compound comprises a Lewis acidic zinc metal centre bonded to two identical or different C1 to C50 hydrocarbon radicals (R1, R2).

2. A process according to claim 1, wherein the C1 to C50 hydrocarbon radicals are linear, branched or cyclic.

3. A process according to claim 1, wherein the C1 to C50 hydrocarbon radicals comprise aryl groups or substituted aryl groups.

4. A process according to any one of claims 1-3, wherein said isoolefin monomer comprises isobutene.

5. A process according to any one of claims 1-4, wherein the process is conducted in the presence of at least one activator of the general formula R3CX (I) or RCOX (II) with each R independently being a C1 to C50 hydrocarbon radical and each X being a halogen.

6. A process according to any one of claims 1-5, wherein said monomer units comprise isobutene and isoprene.

7. A process according to any one of claims 1-6, wherein said process is a slurry polymerisation.

8. A process according to claim 6, wherein said monomer units comprise further copolymerizable monomers.